Frequency diversity is a well known technique in the prior art that can be used for better channel adaptation and also for interference mitigation means.
Frequency diversity is a known method for don't-put-all-your-eggs-in-one-basket motivated communications, since any individual fixed frequency may be plagued by noise, interference and so forth. Some protocols provide a certain level of frequency diversity which may or may not be sufficient for particular applications while others provide none.
For example, in the next cellular standard after LTE, the LTE-Advanced, several carriers are used simultaneously for frequency diversity and also to achieve higher throughputs. However, supporting several concurrent channels is difficult to implement because in order to do so, one needs to have multi-channel hardware at both ends (a transmitter and a receiver), which is not a simple task, especially at the handset (mobile station) side. Therefore, there is a need for frequency diversity capability, with easier implementation.
Many communication systems typically use a fixed center frequency. In example, some wireless cellular communication systems such as 2G (CDMA) 3G (WCDMA) and 4G (WiMax, LTE) uses typically fixed center frequency for communications within the cell. Sometimes all cellular networks can be operated using a single fixed center frequency (in case of frequency reuse=1).
Addition of frequency diversity to such systems (having fixed center frequency) can give these systems great advantage, as described above.
In most cases, addition of the frequency diversity ability inside existing equipment (off-the-shelf) can be complex and costly. However, use of an external apparatus allows using various types of off-the-shelf equipment (without any development efforts) from different equipment suppliers.
Therefore, an add-on (external to the transmitter and receiver) apparatus and relevant methods, that enable the addition of frequency diversity ability to communication systems not having such ability, is needed.
It is known that as a communication system moves from one center frequency to another, there is a transient time period which is prone to error, typically both at the transmitter end and at the receiver end, due to the “settling time” required by the hardware to adjust to the new frequency.
A variety of frequency converters are prevalent in the art.
Layer 1, 2 and 3 relays are known.
Many different communication protocols such as LTE, 3G UMTS, WiMAX, WiFi, OFDMA, CDMA and TDMA are known.
Receivers which recognize elements of a known protocol, such as cyclic prefixes, are known.
The disclosures of all publications and patent documents mentioned in the specification, and of the publications and patent documents cited therein directly or indirectly, and of specifications of mentioned protocols are hereby incorporated by reference.
Algorithms which lock onto the frequency of a signal are known. These algorithms tend to be more successful when operating on simple signals, or signals having statistical characteristics selected to facilitate rapid measurement of frequency. For example, these algorithms tend to be more successful when operating on CW signals, as opposed to complex information-carrying signals.